The present invention generally pertains to measurement of physiological properties and is particularly directed to a method and system of electrocardiographic signal processing.
It is known that a myocardial infarction decreases the quantity of functioning tissue in the heart muscle. It is also known that a therapeutic intervention following a myocardial infarction causes a portion of the tissue in the heart muscle rendered non-functioning by the infarction to again function and thereby prevent such restored tissue from dying.
It is one object of the present invention to provide means for ascertaining the percentage of heart muscle tissue affected by an intervention. The term"intervention" when used by itself herein, refers to either a myocardial infarction or a therapeutic intervention.
It is a further object of the present invention to provide novel apparatus for electrocardiographic signal processing.
Measurements related to the functioning of the heart muscle typically are made by electrocardiographic techniques. Such electrocardiographic techniques such as vectorcardiogram signal processing are used in diagnosing myocardial infarctions. The vectorcardiogram approach is premised on an assumption that upon each contraction of the heart muscle, a sheet of electrical depolarization traverses the heart muscle, thereby providing detectable changes in electrical potential. Through the use of electrodes attached to the body, vectorcardiogram signals x(t), y(t), and z(t), hereinafter referred to as X, Y and Z, are provided. The vectorcardiogram signals are representative of the electrical potential on the surface of the body produced by the transversal of the depolarization sheet within the heart muscle. Through the use of an analog computer vectorcardiograms have been produced and analyzed. The spatial magnitude vector cardiogram .sqroot.X.sup.2 + Y.sup.2 + Z.sup.2 and the spatial velocity vectorcardiogram .sqroot.X.sup.2 + Y.sup.2 + Z.sup.2, have been studied in relation to the effects of a myocardial infarction. X, Y, and Z are the first derivatives with respect to time of X, Y, and Z respectively. However, such studies have not so defined that relationship as to be able to make a quantitative determination of the proporation of heart muscle tissue affected by an intervention.